Effects of organic pollutants on struvite crystallization kinetics and the molecular mechanism of inhibition on crystal growth

Menghui Yao; Lingyu Wang; Jiahao Wei; Zhenkai Cen; Xuemei Wei; Guoqi Yu; Hualiang Shen; Runpu Shen; Dandan Han; Mingyang Chen; Kangli Li; Junbo Gong

doi:10.1016/j.scitotenv.2023.164882

Effects of organic pollutants on struvite crystallization kinetics and the molecular mechanism of inhibition on crystal growth

Sci Total Environ. 2023 Oct 10:894:164882. doi: 10.1016/j.scitotenv.2023.164882. Epub 2023 Jun 16.

Authors

Menghui Yao¹, Lingyu Wang¹, Jiahao Wei¹, Zhenkai Cen¹, Xuemei Wei², Guoqi Yu², Hualiang Shen², Runpu Shen², Dandan Han³, Mingyang Chen⁴, Kangli Li⁵, Junbo Gong³

Affiliations

¹ State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People's Republic of China.
² Zhejiang Engineering Research Center of Fat-soluble Vitamin, Shaoxing University, Shaoxing, Zhejiang 312000, People's Republic of China.
³ State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People's Republic of China; Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, People's Republic of China; Zhejiang Institute of Tianjin University, Shaoxing, Zhejiang 312300, People's Republic of China.
⁴ State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People's Republic of China; Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, People's Republic of China; Zhejiang Institute of Tianjin University, Shaoxing, Zhejiang 312300, People's Republic of China. Electronic address: chenmingyang@tju.edu.cn.
⁵ State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People's Republic of China; Zhejiang Institute of Tianjin University, Shaoxing, Zhejiang 312300, People's Republic of China. Electronic address: kangli_li@163.com.

PMID: 37329921
DOI: 10.1016/j.scitotenv.2023.164882

Abstract

The abilities of improving phosphorus (P) resources sustainability and reducing water eutrophication make struvite crystallization technology attract increasing interest in wastewater treatment, but struvite crystallization process may be affected by various impurities in wastewater. In this study, the effects of nine representative ionic surfactants including three types (anionic, cationic and zwitterionic) on crystallization kinetics and product quality of struvite were investigated, and the influencing mechanism was further probed. The results demonstrated that anionic surfactants significantly inhibit crystal growth so as to reduce crystal size especially in a-axis direction, change crystal morphology and decrease P recovery efficiency, and also lead to a slight decline in product purity. In contrast, cationic and zwitterionic surfactants have no obvious influence on the formation of struvite. A series of experimental characterizations and molecular simulations collectively revealed that the inhibition of crystal growth by anionic surfactants is attributed to the adsorption of anionic surfactant molecules on struvite crystal surface and subsequent blockage of active growth sites. The binding ability of surfactant molecules with the Mg²⁺ exposed on struvite crystal surface was highlighted to be the most essential factor determining the adsorption behavior and adsorption capacity. Anionic surfactants with stronger binding ability with Mg²⁺ have more intense inhibitory effect, but a large molecular volume of anionic surfactants will weaken the adsorption capacity on crystal surface so as to reduce the inhibitory effect. Contrastively, cationic and zwitterion surfactants without binding ability with Mg²⁺ have no inhibitory effect. These findings enable us to have a clearer understanding of the impact of organic pollutants on struvite crystallization and make a preliminary judgment on the organic pollutants that may have the ability to inhibit the crystal growth of struvite.

Keywords: Computational chemistry; Organic pollutants; Phosphorus recovery; Struvite crystallization; Wastewater treatment.